The raw materials for calcination are crushed and screened to obtain particles of 10-30 mm. Maintaining a constant particle size is crucial for maintaining normal electrical conductivity and other electrical parameters within the furnace. At the beginning of calcination, because the raw material has a high electrical resistance, approximately one-third of the pre-calcined material should be added to the furnace bottom. Raw material is then added from a hopper located at the top of the furnace until the furnace is full. The electrode tips should be buried 300-500 mm deep in the material to prevent oxidation of the electrodes and the raw material in the high-temperature area.
When the material is still unheated, its resistance is high, so the voltage should be increased to ensure a certain current flows. As the material temperature rises, the resistance gradually decreases, and the current increases. At this point, the voltage is adjusted according to the specified current. When the current reaches the specified value, indicating that the material temperature in the furnace has reached the required level, the material can be discharged. New material is added, and the current decreases again. The amount and interval of discharges depend on the true density of the material; generally, discharges are performed every 20 minutes.
The voltage, current, discharge time, and discharge quantity are mutually constrained. Production control primarily focuses on adjusting the current and controlling the discharge time. In addition to adjusting the voltage to increase or decrease the current, the electrode suspension height can also be adjusted to control the resistance within the furnace.
Electric calciners feature a simple and compact structure, continuous and convenient operation, and a high degree of automation, making them particularly suitable for burning anthracite. However, their disadvantages include the fact that volatile matter released from the calcined material during the calcination process cannot be fully utilized and is instead discharged. This results in low furnace capacity and production capacity, high energy consumption, significant oxidation and burnout of the material, and uneven calcination quality.